select.c revision 290001 
1/*	$OpenBSD: select.c,v 1.2 2002/06/25 15:50:15 mickey Exp $	*/
2
3/*
4 * Copyright 2000-2007 Niels Provos <provos@citi.umich.edu>
5 * Copyright 2007-2012 Niels Provos and Nick Mathewson
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. The name of the author may not be used to endorse or promote products
16 *    derived from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29#include "event2/event-config.h"
30#include "evconfig-private.h"
31
32#ifdef EVENT__HAVE_SELECT
33
34#ifdef __APPLE__
35/* Apple wants us to define this if we might ever pass more than
36 * FD_SETSIZE bits to select(). */
37#define _DARWIN_UNLIMITED_SELECT
38#endif
39
40#include <sys/types.h>
41#ifdef EVENT__HAVE_SYS_TIME_H
42#include <sys/time.h>
43#endif
44#ifdef EVENT__HAVE_SYS_SELECT_H
45#include <sys/select.h>
46#endif
47#include <sys/queue.h>
48#include <signal.h>
49#include <stdio.h>
50#include <stdlib.h>
51#include <string.h>
52#include <unistd.h>
53#include <errno.h>
54
55#include "event-internal.h"
56#include "evsignal-internal.h"
57#include "event2/thread.h"
58#include "evthread-internal.h"
59#include "log-internal.h"
60#include "evmap-internal.h"
61
62#ifndef EVENT__HAVE_FD_MASK
63/* This type is mandatory, but Android doesn't define it. */
64typedef unsigned long fd_mask;
65#endif
66
67#ifndef NFDBITS
68#define NFDBITS (sizeof(fd_mask)*8)
69#endif
70
71/* Divide positive x by y, rounding up. */
72#define DIV_ROUNDUP(x, y)   (((x)+((y)-1))/(y))
73
74/* How many bytes to allocate for N fds? */
75#define SELECT_ALLOC_SIZE(n) \
76	(DIV_ROUNDUP(n, NFDBITS) * sizeof(fd_mask))
77
78struct selectop {
79	int event_fds;		/* Highest fd in fd set */
80	int event_fdsz;
81	int resize_out_sets;
82	fd_set *event_readset_in;
83	fd_set *event_writeset_in;
84	fd_set *event_readset_out;
85	fd_set *event_writeset_out;
86};
87
88static void *select_init(struct event_base *);
89static int select_add(struct event_base *, int, short old, short events, void*);
90static int select_del(struct event_base *, int, short old, short events, void*);
91static int select_dispatch(struct event_base *, struct timeval *);
92static void select_dealloc(struct event_base *);
93
94const struct eventop selectops = {
95	"select",
96	select_init,
97	select_add,
98	select_del,
99	select_dispatch,
100	select_dealloc,
101	0, /* doesn't need reinit. */
102	EV_FEATURE_FDS,
103	0,
104};
105
106static int select_resize(struct selectop *sop, int fdsz);
107static void select_free_selectop(struct selectop *sop);
108
109static void *
110select_init(struct event_base *base)
111{
112	struct selectop *sop;
113
114	if (!(sop = mm_calloc(1, sizeof(struct selectop))))
115		return (NULL);
116
117	if (select_resize(sop, SELECT_ALLOC_SIZE(32 + 1))) {
118		select_free_selectop(sop);
119		return (NULL);
120	}
121
122	evsig_init_(base);
123
124	evutil_weakrand_seed_(&base->weakrand_seed, 0);
125
126	return (sop);
127}
128
129#ifdef CHECK_INVARIANTS
130static void
131check_selectop(struct selectop *sop)
132{
133	/* nothing to be done here */
134}
135#else
136#define check_selectop(sop) do { (void) sop; } while (0)
137#endif
138
139static int
140select_dispatch(struct event_base *base, struct timeval *tv)
141{
142	int res=0, i, j, nfds;
143	struct selectop *sop = base->evbase;
144
145	check_selectop(sop);
146	if (sop->resize_out_sets) {
147		fd_set *readset_out=NULL, *writeset_out=NULL;
148		size_t sz = sop->event_fdsz;
149		if (!(readset_out = mm_realloc(sop->event_readset_out, sz)))
150			return (-1);
151		sop->event_readset_out = readset_out;
152		if (!(writeset_out = mm_realloc(sop->event_writeset_out, sz))) {
153			/* We don't free readset_out here, since it was
154			 * already successfully reallocated. The next time
155			 * we call select_dispatch, the realloc will be a
156			 * no-op. */
157			return (-1);
158		}
159		sop->event_writeset_out = writeset_out;
160		sop->resize_out_sets = 0;
161	}
162
163	memcpy(sop->event_readset_out, sop->event_readset_in,
164	       sop->event_fdsz);
165	memcpy(sop->event_writeset_out, sop->event_writeset_in,
166	       sop->event_fdsz);
167
168	nfds = sop->event_fds+1;
169
170	EVBASE_RELEASE_LOCK(base, th_base_lock);
171
172	res = select(nfds, sop->event_readset_out,
173	    sop->event_writeset_out, NULL, tv);
174
175	EVBASE_ACQUIRE_LOCK(base, th_base_lock);
176
177	check_selectop(sop);
178
179	if (res == -1) {
180		if (errno != EINTR) {
181			event_warn("select");
182			return (-1);
183		}
184
185		return (0);
186	}
187
188	event_debug(("%s: select reports %d", __func__, res));
189
190	check_selectop(sop);
191	i = evutil_weakrand_range_(&base->weakrand_seed, nfds);
192	for (j = 0; j < nfds; ++j) {
193		if (++i >= nfds)
194			i = 0;
195		res = 0;
196		if (FD_ISSET(i, sop->event_readset_out))
197			res |= EV_READ;
198		if (FD_ISSET(i, sop->event_writeset_out))
199			res |= EV_WRITE;
200
201		if (res == 0)
202			continue;
203
204		evmap_io_active_(base, i, res);
205	}
206	check_selectop(sop);
207
208	return (0);
209}
210
211static int
212select_resize(struct selectop *sop, int fdsz)
213{
214	fd_set *readset_in = NULL;
215	fd_set *writeset_in = NULL;
216
217	if (sop->event_readset_in)
218		check_selectop(sop);
219
220	if ((readset_in = mm_realloc(sop->event_readset_in, fdsz)) == NULL)
221		goto error;
222	sop->event_readset_in = readset_in;
223	if ((writeset_in = mm_realloc(sop->event_writeset_in, fdsz)) == NULL) {
224		/* Note that this will leave event_readset_in expanded.
225		 * That's okay; we wouldn't want to free it, since that would
226		 * change the semantics of select_resize from "expand the
227		 * readset_in and writeset_in, or return -1" to "expand the
228		 * *set_in members, or trash them and return -1."
229		 */
230		goto error;
231	}
232	sop->event_writeset_in = writeset_in;
233	sop->resize_out_sets = 1;
234
235	memset((char *)sop->event_readset_in + sop->event_fdsz, 0,
236	    fdsz - sop->event_fdsz);
237	memset((char *)sop->event_writeset_in + sop->event_fdsz, 0,
238	    fdsz - sop->event_fdsz);
239
240	sop->event_fdsz = fdsz;
241	check_selectop(sop);
242
243	return (0);
244
245 error:
246	event_warn("malloc");
247	return (-1);
248}
249
250
251static int
252select_add(struct event_base *base, int fd, short old, short events, void *p)
253{
254	struct selectop *sop = base->evbase;
255	(void) p;
256
257	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
258	check_selectop(sop);
259	/*
260	 * Keep track of the highest fd, so that we can calculate the size
261	 * of the fd_sets for select(2)
262	 */
263	if (sop->event_fds < fd) {
264		int fdsz = sop->event_fdsz;
265
266		if (fdsz < (int)sizeof(fd_mask))
267			fdsz = (int)sizeof(fd_mask);
268
269		/* In theory we should worry about overflow here.  In
270		 * reality, though, the highest fd on a unixy system will
271		 * not overflow here. XXXX */
272		while (fdsz < (int) SELECT_ALLOC_SIZE(fd + 1))
273			fdsz *= 2;
274
275		if (fdsz != sop->event_fdsz) {
276			if (select_resize(sop, fdsz)) {
277				check_selectop(sop);
278				return (-1);
279			}
280		}
281
282		sop->event_fds = fd;
283	}
284
285	if (events & EV_READ)
286		FD_SET(fd, sop->event_readset_in);
287	if (events & EV_WRITE)
288		FD_SET(fd, sop->event_writeset_in);
289	check_selectop(sop);
290
291	return (0);
292}
293
294/*
295 * Nothing to be done here.
296 */
297
298static int
299select_del(struct event_base *base, int fd, short old, short events, void *p)
300{
301	struct selectop *sop = base->evbase;
302	(void)p;
303
304	EVUTIL_ASSERT((events & EV_SIGNAL) == 0);
305	check_selectop(sop);
306
307	if (sop->event_fds < fd) {
308		check_selectop(sop);
309		return (0);
310	}
311
312	if (events & EV_READ)
313		FD_CLR(fd, sop->event_readset_in);
314
315	if (events & EV_WRITE)
316		FD_CLR(fd, sop->event_writeset_in);
317
318	check_selectop(sop);
319	return (0);
320}
321
322static void
323select_free_selectop(struct selectop *sop)
324{
325	if (sop->event_readset_in)
326		mm_free(sop->event_readset_in);
327	if (sop->event_writeset_in)
328		mm_free(sop->event_writeset_in);
329	if (sop->event_readset_out)
330		mm_free(sop->event_readset_out);
331	if (sop->event_writeset_out)
332		mm_free(sop->event_writeset_out);
333
334	memset(sop, 0, sizeof(struct selectop));
335	mm_free(sop);
336}
337
338static void
339select_dealloc(struct event_base *base)
340{
341	evsig_dealloc_(base);
342
343	select_free_selectop(base->evbase);
344}
345
346#endif /* EVENT__HAVE_SELECT */
347